This invention relates to a system for selectively interconnecting a plurality of communication lines to provide communication therebetween and, in particular, to a system capable of dealing with both of a data signal and a speech signal.
Various systems have been proposed for selectively distributing digital signals among a plurality of communication lines. A typical system is disclosed in U.S. Pat. No. 4,601,029 issued to Franklin Hargrave et al. In this conventional system, each communication port, through which communication signals are transmitted and received, is assigned with transmitting time slots on a transmission bus and receiving time slots on a reception bus. Communication is carried out by the use of the transmitting and receiving time slots.
In order to carry out intercommunication or two-way communication through two communication ports, the above-mentioned conventional system requires two transmission time slots on the transmission bus and two receiving time slots on the reception bus in the manner known in the art. In this connection, these buses can not be fully efficiently used. For example, it is assumed that a single frame consists of twenty-four time slots in each of the transmission and the reception buses. In this event, only twelve pairs of the communication ports can simultaneously carry out intercommunication through each pair.
In addition, it is impossible for the conventional switching system to deal with a particular signal having a transmission speed which is lower than that of a speech signal.